JP3535606B2 - Water absorbing sheets and bags for food - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material having a property of absorbing water, and relates to a water-absorbing sheet and a water-absorbing bag which can be used for maintaining freshness of fresh foods by dehydration and drying and improving taste.

[0002]

2. Description of the Related Art Conventionally, as a water absorbent sheet,
Paper, cloth, non-woven fabric, etc. have been used, but they have drawbacks such as low water absorption, weak water retention, and liberation of water due to external stimulation. Further, there is also one in which a super absorbent polymer is sandwiched between paper and a non-woven fabric, but it is difficult to uniformly support the super absorbent polymer on a non-woven fabric since it is in a powder form.

In response to these problems, dehydration sheets utilizing osmotic pressure have been developed mainly for foods (Japanese Patent Publication No. Sho 5).
8-58124, etc.). By applying or encapsulating a high-concentration solution of saccharides and an acrylic acid-based polymer absorbent on a semi-permeable membrane, they utilize the osmotic pressure of the high-concentration solution and the water absorption capacity of the polymer absorbent to achieve strong dehydration. It is to gain strength. However, since a high-concentration solution of saccharides has a high viscosity, it is difficult to handle during the production, and bubbles are not completely removed in the finished product, which is a problem in appearance.

The applicant of the present invention has previously proposed a water-absorbent sheet in which a water-absorbent film mainly containing ethylene oxide is used as a water-absorbent material, and the film is covered with a semipermeable polyvinyl alcohol film. It has excellent water absorption, is easy to manufacture, has a good appearance, and is extremely suitable for dehydration and freshness preservation of fresh foods. However, the problem here is that elution from the water-absorbent material by water is considered. As a material to be used with food, it is desirable that the amount eluted into water is as small as possible.

In the above water-absorbing sheet, the material that comes into direct contact with food is a semi-permeable film, but by any chance a semi-permeable film may have pinholes, or a hard food or a sharp food. When water is dehydrated, it is expected that the food will damage the semipermeable membrane and the food and the water-absorbent film will come into direct contact with each other. Therefore, it is desirable that the water-absorbent film also has the smallest elution amount.

[0006]

SUMMARY OF THE INVENTION The present invention has been made based on such a background, and provides a water-absorbent sheet for foods, which has a high water-absorbing capacity and an extremely small amount of water to be eluted, and its summary Is a water-absorbent sheet for food, which is obtained by coating a water-absorbent film containing a water-absorbent polymer compound composed of a repeating unit represented by the following general formula (1) with a semipermeable polyvinyl alcohol film. It is in.

[0007]

[Chemical 3] Further, in the present invention, a water absorbent sheet for food, which is obtained by fusion-bonding the water absorbent film to a semipermeable membrane polyvinyl alcohol film, and a water absorbent sheet as described above, with the semipermeable membrane polyvinyl alcohol film as an inner surface. Provided is a water-absorbent bag for food, which is formed into a bag.

The present invention will be described in detail below. The water-absorbent sheet or bag for foods of the present invention comprises a semi-permeable polyvinyl alcohol film and a water-absorbent film having a special structure as essential components.

This polyvinyl alcohol (sometimes abbreviated as PVA hereinafter) film comes to the side that comes into contact with food when used, and has a strong affinity for water but is insoluble in water, and has a water molecule and odor. It has a semipermeable property that allows components to pass through but does not allow umami components with large molecules to pass through. Such a film can be obtained by forming a film of completely saponified polyvinyl alcohol. The PVA film may contain a plasticizer such as glycerin for imparting flexibility.

The water-absorbent film is mainly composed of a water-absorbent polymer compound composed of the repeating unit represented by the above general formula (1). In the above formula (1),
The addition form of the alkylene oxide chain portion represented by A is
The ethylene oxide chain represented by the repeating unit m and the ethylene oxide chain represented by the repeating unit p are located at both terminals with the α-olefin oxide chain represented by the repeating unit n having 12 or more carbon atoms sandwiched therebetween. .

Two ethylene oxide chains account for 90 to 94% by weight (hereinafter "%") in the alkylene oxide chain portion.
Abbreviated), and 6 to 10% by weight of α-olefin oxide chain having 12 or more carbon atoms is present. In short, the weight ratio calculated from these repetition numbers m, n, p is (molecular weight of ethylene oxide: 44) (m + p) / (carbon number 12
The above-mentioned molecular weight of α-olefin oxide) n = 94/6
It is set to be 90/10. If the two ethylene oxide chains are less than 90%, the water absorption will decrease, and conversely 94
If it exceeds%, the amount eluted into water increases.

Further, in the ethylene oxide chain represented by the repeating unit p, which is bonded to the dicarboxylic acid compound residue which is R ₂ , p / (m + n) is preferably set to 50% or more. That is, when the repeating portion p is set to 50% or more of the total amount of the two ethylene oxide chains (repeating portions m and p), the polyesterification reaction and the polyester exchange reaction are facilitated.

The water-absorbing polymer compound represented by the above (1) can be obtained by using the following two components (A) and (B). (A) Ethylene oxide is addition-polymerized to an organic compound having two active hydrogen groups, and then α-containing 12 or more carbon atoms.
Weight average molecular weight of 5,000 obtained by addition-polymerizing olefin oxide and further ethylene oxide
~ 30,000 alkylene oxide compounds. (B) Dicarboxylic acid compound.

Examples of the organic compound having two active hydrogen groups include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol,
Examples thereof include bisphenol A, butylamine, aniline, polytetramethylene glycol and the like.

In the above (A), the α-olefin oxide having 12 or more carbon atoms used as a compound to be addition-polymerized with ethylene oxide is particularly limited as long as it is an epoxide compound having an alkylene group having 10 or more carbon atoms. But more preferably an epoxide compound having an alkylene group having 12 to 30 carbon atoms. In addition, ethylene oxide and α-olefin oxide having 12 or more carbon atoms, which are added to an organic compound having two active hydrogen groups in three stages, have a total ethylene oxide content of 90 to 94% of the total,
The total amount of α-olefin oxide having 12 or more carbon atoms is 6
Set to -10%.

In the above (A), ethylene oxide, α-olefin oxide having 12 or more carbon atoms and ethylene oxide are sequentially added in a block form using the above components at a temperature of about 90 to 200 ° C. using caustic alkali as a catalyst. It is obtained by polymerizing and has a weight average molecular weight of 5,
It is preferably set to 000 to 30,000.

Examples of the dicarboxylic acid compound (B) include dicarboxylic acid, dicarboxylic anhydride, and lower alkyl ester of dicarboxylic acid. Examples of the dicarboxylic acid include phthalic acid, isophthalic acid, terephthalic acid,
Malonic acid, sebacic acid, fumaric acid, adipic acid, etc. are mentioned, and these dicarboxylic acid anhydrides are mentioned. Examples of the lower alkyl ester of dicarboxylic acid include methyl ester, dimethyl ester, ethyl ester, diethyl ester of the above various dicarboxylic acids,
There is propyl ester.

The water-absorbing polymer compound used in the present invention can be obtained by adding (B) to the above (A) and dehydrating or dealcoholizing under heating and reduced pressure. The water-absorbing polymer compound thus obtained preferably has a weight average molecular weight of 15,000 to 300,000.

The water-absorbent sheet of the present invention is prepared by molding the above water-absorbent polymer compound into a film. As a method for producing a film, there are a melt extrusion method, a calender method and the like, and particularly, a film can be easily formed by melt extrusion molding.

The form of the water absorbent sheet for food of the present invention will be described below. One embodiment of the water absorbent sheet for food of the present invention is one in which a water absorbent film is housed in a bag of a semipermeable membrane PVA film. That is, it is obtained by sandwiching a water-absorbent film between two sheets of semipermeable membrane PVA film and heat-sealing the four sides of the semipermeable membrane PVA film. This water absorbing sheet is a sheet-like thin overall,
Good appearance and easy to manufacture. Then, it can be used under the food or wrapped around the food. Water is absorbed by the water absorbent resin film through the semipermeable membrane PVA film in contact with the food, but the umami component of the food remains without permeation.

In another embodiment, a water absorbent film is fused and laminated on a semipermeable membrane PVA film. During use, water is absorbed by the water-absorbent resin film through the semipermeable membrane PVA film that is in contact with food, but the PVA film and the water-absorbent resin film are fused and laminated at this time, and a gap is formed between both layers. Since it does not occur and there is no layer such as an adhesive that inhibits moisture permeation, it has an advantage of increasing the water absorption rate.

In this embodiment, a semipermeable membrane PVA film can be laminated on the other surface of the water absorbent film.
Further, a non-water-permeable plastic film, for example, a film made of polyethylene, polypropylene, ethylene-vinyl acetate copolymer resin, polyethylene terephthalate or the like can be laminated on the other surface of the water-absorbent film. These 3
The layered water-absorbent sheet prevents moisture absorbed from food from seeping out to the outer surface, imparts an appropriate level of rigidity to the entire water-absorbent sheet to facilitate handling, and further prevents odors and water from the outside. It has advantages such as no damage even if it is damaged, moisture resistance, and prevention of blocking between sheets.

The laminated water-absorbent sheet, or the water-absorbent sheet having a semipermeable membrane PVA film or a non-permeable plastic film added thereto, has a semipermeable membrane PVA film or a non-permeable membrane on the outer surface side and / or the side in contact with food. The water-based plastic film may be partially fixed and laminated on the water-absorbent film.

As a result, the flexibility of the water absorbent sheet as a whole is increased, curling at the time of water absorption is prevented, and the water absorbing ability of the water absorbent sheet can be sufficiently exhibited. That is, since the water-absorbent film expands when it absorbs water, if a non-water-permeable plastic film or the like is stuck on the entire surface, the whole tends to curl, and as a result of suppressing the water-absorption expansion of the water-absorbent resin film, the water absorption speed or The amount of water absorption may decrease. As a method of partially fixing, dot-like, linear,
There is a method of heat fusion bonding or adhesive bonding in a lattice shape. Here, it is appropriate that the fixing area is about 5 to 50% of the whole, and if this area is less than 5%, the fixing strength will be insufficient, and if it exceeds 50%, the effect of curl prevention will be insufficient and partial fixing will occur. Meaningless. It is preferable that the fixing portion is uniformly dispersed and provided, and as the fixing method, fusion bonding similar to the above is practical.

As a method for laminating the water-absorbent film on the PVA film, there is a method of thermocompression-bonding the water-absorbent film and the PVA film, which have been previously formed into a film as described above, by a nickel roll or a press plate. In this case, 60 to 10
Since the water-absorbent film is melted and fused to the PVA film at a low temperature of about 0 ° C., the PVA film is not adversely affected by heat. As another method, there is a method of coating the PVA film while extruding the molten water-absorbent resin into a film shape.

Further, when the non-water-permeable film is laminated on the back surface of the water-absorbent film, it can be produced according to the above method, and the water-absorbent film and the non-water-permeable film are co-extruded to form a two-layer film of the PVA film. It can also be laminated. When the water-absorbent film and the PVA film or the non-water-permeable film are laminated by a partially fixed portion, for example, a process such as engraving on a nip roll or a press plate for lamination to give unevenness, and not the entire surface Therefore, it is possible to fix only appropriate portions.

As yet another aspect of the present invention, there is provided a water absorbent bag for foods, which is made by bag-making the water absorbent sheet having various laminated structures described above with the semipermeable membrane PVA film as an inner surface. The bag is used by putting food in it, and since the whole bag is in a bag shape, the food is kept hygienic, and even if it is used in a refrigerator or the like, there is no odor transfer. In order to make the laminated water-absorbing sheet into a bag, it is convenient to use a general heat sealing method, and a so-called gas-sealing type seal in which the semipermeable membrane PVA films on the inner surface of the bag are joined together may be used. Alternatively, a so-called envelope sticking seal in which the semipermeable membrane PVA film on the inner surface and the water absorbent resin film on the outer surface are joined together may be used. Even when a non-water-permeable film such as polyethylene is laminated, it can be easily heat-sealed with the PVA film or the water-absorbing film.

This water-absorbent bag is used with the PVA film inside and the food inside. However, since the PVA film is inside, when the PVA film comes into contact with water or drip present on the surface of the food, the PVA film naturally comes into contact with the food. Etc. After the food is put, the mouth of the bag can be closed with an adhesive tape or a ligature wire, or a removable adhesive can be applied to the mouth of the bag for sealing. It may also be a bag with a check.

In the various embodiments exemplified above, the thickness of each layer can be appropriately set according to the application, but one example is P
When the VA film is thin, it lacks strength and stiffness, and it tends to have wrinkles, resulting in poor processability, and when it is too thick, it impairs water permeability. Therefore, in consideration of these points, the range of 5 to 25 μm is preferable. Further, the thicker the water-absorbent film is, the more excellent the water-absorbing performance is, but on the other hand, the usability is deteriorated.
Is preferred. Furthermore, when a non-water-permeable film is used, it is preferable to make it as thin as possible, and in view of workability, the thickness can be set to about 10 to 50 μm.

INDUSTRIAL APPLICABILITY The water absorbent sheet and bag for foods of the present invention are useful for removing excess water and odor from fresh foods and absorbing drip generated during thawing of frozen foods. It is also suitable for commercial use in cafeterias and for cooking at home.

[0031]

EXAMPLES Specific examples will be described below with reference to examples. The performance evaluation method is as follows. 1) Elution amount with respect to water a) Potassium permanganate consumption A sheet with an area of 150 cm ² is distilled with 300 cc of distilled water at 60 ° C.
It was dipped in a beaker containing the soup for 30 minutes while maintaining the temperature, and then rapidly filtered to collect a filtrate, and the potassium permanganate consumption of the filtrate was measured. b) Evaporation residue The above filtrate was concentrated and dried, and the weight of the residue was determined.

2) The weight a (g) of the film having a water absorption capacity of 5 cm × 5 cm before water absorption is measured. Then, use the film as distilled water 250 at 25 ° C.
After immersing in a beaker containing cc for 30 minutes, the beaker was taken out and allowed to stand until there was no drop of water, and the weight b (g) after water absorption was measured, and (ba) / a was taken as the water absorption capacity.

Example 1 Addition polymerization of ethylene oxide with ethylene glycol was carried out, and then α-olefin oxide (mixture of epoxide compound having 12 and 14 carbon atoms, molecular weight 196) was added and further ethylene oxide was added and polymerized. 1.9 parts of dimethyl sebacate was added to the polyalkylene oxide compound (weight average molecular weight 13,000), and transesterification reaction was performed to obtain a water-absorbing polymer compound having a weight average molecular weight of 120,000. The water-absorbing polymer compound was composed of the repeating unit represented by the general formula (1), and X, R ₂ , m, n and p were as follows. Further, in A of the formula (1), the number of repetitions m, n, p
The weight ratio calculated from is 44 (m + p) / 196n =
It was 94/6.

Further, in A of the formula (1), the number of repetitions m, n,
The weight ratio calculated from p is 44 (m + p) / 196n
= 94/6, and p / (m + n) = 60% in the weight ratio calculated from the repeating units m and p.

[0035]

[Chemical 4] In addition, a water-absorbing polymer compound was obtained in the same manner as above except that the weight ratio of ethylene oxide and the α-olefin oxide was changed. These water-absorbing polymer compounds were extruded by an extruder at a T-die temperature of 120 ° C. to obtain a water-absorbing film having a thickness of 50 μm, the consumption amount of potassium permanganate and the evaporation residue were measured, and the water absorption capacity was also measured. .

For comparison, dimethyl terephthalate was added to a polyalkylene oxide compound obtained by addition-polymerizing ethylene oxide to ethylene glycol, and transesterification reaction was performed to obtain a water-soluble polymer compound having a weight average molecular weight of 130,000. Then, a film with a thickness of 50 μm is made from the water-soluble polymer compound as described above, and γ
The line was irradiated with an absorbed dose of 10 Mrad and crosslinked to obtain a water-absorbent film, and the same measurement was performed. The results are shown in Table 1.
Shown in.

[0037]

[Table 1]

As is clear from this result, No. 1 having the characteristics within the range specified in the present invention. Nos. 1 and 2 have sufficient water absorbency and a potassium permanganate consumption of 10
The elution amount with respect to water was extremely small, such as ppm or less and 30 ppm or less in the evaporation residue.

(Embodiment 2) No. 1 of the first embodiment. Using the water-absorbent film of No. 1 (thickness: 50 μm), the following water-absorbent sheet or bag for foods is prepared, and the water-absorbent sheet or bag is prepared by the following method.
The grated eel was wrapped and stored in a refrigerator (4 ° C. × 66% RH) to measure the weight change of the eel.

For comparison, the same test was carried out using a commercially available dehydrated sheet (semipermeable membrane of polyvinyl alcohol film in which edible sugar, sizing agent and alcohol were enclosed). Table 2 shows the relationship between the resulting storage time and the change in the weight of the eel. Water-absorbent sheet A A water-absorbent film (200 mm × 400 mm) was sandwiched between two semi-permeable polyvinyl alcohol films (thickness 15 μm), which were slightly larger, and heat-sealed on all sides. This sheet was folded in two, sandwiched with crocodile, put in a polyethylene bag, and stored in a refrigerator.

Water-absorbent sheet B Semi-permeable polyvinyl alcohol film (thickness: 15 μ) was applied to both sides of the water-absorbent film at a temperature of 6 by a laminator.
Thermocompression bonding was performed at 5 ° C., a linear pressure of 3.0 kg / cm, and a take-up speed of 1.5 m / min to obtain a laminated sheet in which each layer having a thickness of 80 μm was fused. This sheet (200 mm × 400 mm) was folded in two, sandwiched with crocodile, put in a polyethylene bag, and stored in a refrigerator.

Water-absorbent bag C A semi-permeable polyvinyl alcohol film (thickness: 15 μm) is arranged on one side of the water-absorbent film, and a low-density polyethylene film (thickness: 15 μm) is arranged on the other side, and the temperature is set to 65 ° C. with a laminator at a linear pressure. 3.0 kg / cm, take-off speed 1.5 m
A thermo-compression bonding was performed at a speed of 1 / min to obtain a laminated sheet having a thickness of 80 μm and each layer partially fused.

From the laminated sheet, a polyvinyl alcohol film was used as the inner surface and heat-sealed to 200 mm ×
A 200 mm bag was made. I put the eel in the bag and kept it in the refrigerator.

[0044]

[Table 2]

From the results shown in Table 2, it can be seen that the water-absorbent sheet or bags A, B and C of the present invention have a higher water-absorption rate than commercial products and are suitable for dehydration treatment in a short time. In particular, B and C, in which the water-absorbent film was fusion-laminated on the semi-permeable polyvinyl alcohol film, had a high water absorption rate.

[0046]

EFFECTS OF THE INVENTION According to the present invention, a water absorbing sheet having a sufficiently high water absorbing property and a small elution amount with respect to water can be obtained, which is particularly excellent as a water absorbing sheet for foods. In addition, if a water-absorbent film is fused and laminated on a semi-permeable polyvinyl alcohol film, the water absorption speed is high, and if a bag with the semi-permeable polyvinyl alcohol film on the inner surface is formed from that sheet, the water absorption speed is high, and hygiene is good. A bag that does not transfer odor is obtained, and it is more convenient than using it by wrapping it around the food because it is used by putting food etc. inside.

Further, since the product of the present invention is in the form of a flat laminated sheet as a whole, it is convenient for distribution, storage, etc., is easy to handle, and has a good appearance.

Claims (4)

(57) [Claims] 1. A food product obtained by coating a water-absorbent film containing a water-absorbent polymer compound composed of a repeating unit represented by the following general formula (1) as a main component with a semipermeable polyvinyl alcohol film. Water absorbent sheet. [Chemical 1] 2. A water-absorbent film containing a water-absorbent polymer compound as a main component, which is composed of a repeating unit represented by the following general formula (1), is fusion-laminated on a semipermeable polyvinyl alcohol film. Water absorbent sheet for food. [Chemical 2] 3. The water absorbent sheet for foods according to claim 2, wherein a non-water-permeable plastic film is laminated on the other surface of the water absorbent film. 4. A water-absorbent bag for foods, which is made by bag-making the water-absorbent sheet according to claim 2 or 3 with a semipermeable polyvinyl alcohol film as an inner surface.